TV footage of the alleged incident showed Chelsea striker Costa going to retrieve the ball for a throw-in and then appearing to make contact with the steward with his foot.

A Chelsea spokesperson simply said: "Utter nonsense". It is understood that the issue was then dealt with amicably and put to bed.

Referee Anthony Taylor will now make mention of the matter in his match report, but further action would appear highly unlikely.

The incident nonetheless provided yet another negative headline for the beleaguered champions after their dismal season took in a new low.

The Blues, without their under-pressure manager Jose Mourinho due to a stadium ban, were beaten for a seventh time in 12 Barclays Premier League games as they went down 1-0.

Chelsea did actually perform creditably, but luck was not on their side and Marko Arnautovic scored the only goal after 53 minutes.

In Mourinho's absence, Chelsea did not send a representative to speak at the post-match press conference. It is the second time in three games that no member of the coaching staff has spoken to written media after Mourinho shunned duties after the loss at West Ham a fortnight ago.

It was other events at Upton Park that day that led to Mourinho's non-appearance for the game at the Britannia Stadium. The Portuguese was handed a one-match stadium ban for abusive language towards match officials.

And despite suggestions Mourinho may try to circumvent the ban - reviving claims that he hid in a laundry basket when suspended in 2005 - there was no sign of him at the stadium. Club officials said he had remained at the team hotel.

If he watched on TV he will have seen Chelsea slip to a third successive league defeat for the first time in 16 years. It was a result that turned the heat up on the manager considerably.

Asked about Mourinho's position, goalkeeper Asmir Begovic, who did speak to TV reporters, told the BBC: "That is out of our hands, we are behind the manager - you can see that from our performances. We think he is the right man and someone we work hard for.

"His spirit and his presence is always there, we wanted to get a result for him."

One the matter of the stadium ban, Begovic said: "Jose did the pre-match talk at the hotel and that was it."

Begovic, Stoke's former number one, felt the Blues were unlucky at his old club.

He said: "We definitely did enough to get a result here, but when things aren't going your way you don't get the luck you deserve.

"We hit the post, we slipped over when we had open goals, we are making things hard for ourselves."

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